Final answer:
The major enzyme responsible for the reduction of carbon dioxide during photosynthesis is ribulose bisphosphate carboxylase, commonly known as rubisco, which plays a critical role in the Calvin cycle's carboxylation stage.
Step-by-step explanation:
The major enzyme that catalyses the reduction of carbon dioxide during photosynthesis is called ribulose bisphosphate carboxylase (rubisco). In the Calvin cycle, the enzyme RuBisCO facilitates the carboxylation stage by incorporating CO₂ into an organic molecule known as ribulose biphosphate (RuBP).
This reaction produces a 6-carbon intermediate that quickly breaks down into two molecules of 3-phosphoglycerate (3-PGA). The RuBisCO enzyme is crucial as it initiates the process of carbon fixation in the Calvin cycle, which eventually leads to the production of carbohydrates like glucose.